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Blurring the Line Between Organism and Machine
Microbots Grow Own Muscles from Cells
Self-assembled microrobot developed at UCLA. |
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Nanotechnology researchers at UCLA’s Henry Samueli School of Engineering and Applied Science have created the first self-assembled microrobots powered by living heart muscle.
Viewed under a powerful microscope, each tiny device is composed of a sheath of cardiac muscle grown from rat cells and connected to an arch of gold. Surrounded in a sugar and protein mixture that emulates the body’s natural environment, each contraction and relaxation of the muscle makes the bot shuffle forward.
The development of an integrated device composed of both organism and machine is significant. Not only does the advance open the door to numerous possibilities such as creating artificial limbs or rebuilding severed fingers by growing a patients’ own muscle cells over artificial bones, but it also is a key innovation in helping scientists learn how to mass produce “bio-machines.” Amazingly, the hybrid devices were grown on silicon chips using the principles and some of the same technology now employed to make integrated
circuits.
Researcher Jianzhong Xi |
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“We didn’t want to limit the imagination,” said Jianzhong Xi, a member of the research team responsible for the experiment. “We started with the key idea that we needed a material friendly to the cell. It was important to balance and integrate the system, so we needed a solution that was unique.”
The answer turned out to be the use of a specific kind of polymer. Using chip-industry methods - normally harmful to living cells - a silicon chip was first etched with “supporting beams” before being coated with a biocompatible polymer and then an arched layer of gold. Deposited muscle cells begin to grow on the gold, while the polymer inhibits
random cell growth and acts as a kind of mold. Finally, the polymer is dissolved and the beams securing the device in
place on the chip are snapped away. It’s at that point that the microbot begins to move, drawing energy from the glucose in the surrounding solution.
“I was surprised when I first saw the bots walk and realized that it had worked,” recalled Xi. “Honestly, I had this picture in my head that they would somehow swim. And then I thought - wow, swimming or walking - they’re moving! It was a great moment.”
In the past, researchers have managed to incorporate living muscle tissue into machines, but “transferring muscles from an organism to a micro device manually isn’t really practical,” said Xi. “The living tissue is often damaged because you’re working on such a tiny scale to attach muscle to a minuscule device and make it stay there.” It’s also time-consuming.
Professor Carlo Montemagno |
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But using the method developed by UCLA, once the polymer devices are in place, injecting the liquid culture with heart muscle cells is quickly accomplished. Because the cells attach and grow only on the exposed metal, the
bots are, in a sense, “self-assembling” units - saving time, money, and ensuring that the living tissue remains intact.
“We can make hundreds of thousands as easily as we can create just one,” said Carlo Montemagno, chair of the School’s bioengineering department, who oversees the project.
Muscle-powered microelectromechanical systems, or MEMS, are an attractive option for researchers for many reasons. By feeding on glucose in the blood, these devices could “potentially be used for micro-surgery, maybe clearing plaque build up in arteries, or for a multitude of other future uses,” said Xi.
The bots in their current state can only move in one direction, and they aren’t all that controllable. But with this recent step forward, the team is already working on the next generation of bots that may hold more promise.
Professor Jacob Schmidt |
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What is the next frontier? Montemagno, Xi and Jacob Schmidt, the team that developed the initial microbots, are already working with skeletal muscle to see if the level of control can be increased, which would make the bots more useful for specific tasks.
While the heart muscle beats to an intrinsic rhythm, skeletal muscle must be manipulated to create movement. Xi suggests this could be done with
electricity, which could then be turned on or off to control the bots in a more consistent manner.
Montemagno believes that “such microbots could eventually function as electrical generators that could power tiny, bodily implants, or even to drive mini-electrical generators to power computer chips, among many other possible uses.”
Whatever their future applications, the bots are a dramatic example of the work scientists are already undertaking in the biotech and nanotech worlds.
As researchers continue to learn more about different muscle tissues, growing them and testing them with specific tasks, the process will become more refined and the application options innumerable. The success the team has had with muscles also raises questions about the possibility of incorporating other kinds of cells and tissues into microchips in the future.
NASA, who provided funding for the project, has its own ideas for the bots, including one day using them to repair the outside of the space shuttle while in orbit. Which means with these microbots, the sky may no longer be the limit.
- Melissa Abraham
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